Method of megasonic cleaning of an object

ABSTRACT

A megasonic cleaning method and a megasonic cleaning apparatus are provided. Microcavitation bubbles may be formed by applying an electromotive force to a cleaning solution using a megasonic energy in a separate room from an object to be cleaned. The microcavitation bubbles having a stable oscillation among the formed microcavitation bubbles may be moved to the object to be cleaned. A surface of the object to be cleaned may be cleaned using the microcavitation bubbles having the stable oscillation. Particles attached onto the surface of the object to be cleaned may be effectively removed while preventing pattern damage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority under 35 U.S.C.§§120 and 121 to U.S. application Ser. No. 12/907,642, filed Oct. 19,2010, which claims priority under 35 U.S.C. §119 to Korean PatentApplication No. 10-2010-0052109, filed on Jun. 3, 2010 in the KoreanIntellectual Property Office (KIPO), the disclosure of each of which ishereby incorporated by reference in its entirety.

BACKGROUND

1. Field

Example embodiments relate to a method of megasonic cleaning of anobject and an apparatus for performing the same. More particularly,example embodiments relate to a method of megasonic cleaning ofsemiconductor substrates and photomasks and an apparatus for performingthe same.

2. Description of the Related Art

Generally, a megasonic cleaning mechanism is used in a semiconductormanufacturing process, particularly, it is used in a cleaning process ofsemiconductor substrates and photomasks. According to the megasoniccleaning mechanism, acoustic energy is applied to liquid medium torapidly form and collapse minute bubbles of gases dissolved in themedium to eliminate adhesion force of particles to the semiconductorsubstrates and the photo masks and to remove the particles there from.When radio frequency (RF) power is applied to a piezoelectrictransducer, the particles also may be removed due to fluid kineticsinduced by acoustic waves through fluid.

However, patterns formed on the semiconductor substrates and thephotomasks may be damaged during the particle removing process. When thepower is reduced or frequency is increased to prevent the patterndamages, cleaning efficiency may be reduced.

SUMMARY

Example embodiments provide a method of megasonic cleaning of an object,capable of restraining the pattern damages on semiconductor substratesand photomasks and improving cleaning efficiency.

Example embodiments provide an apparatus for performing the megasoniccleaning method.

In accordance with example embodiments, a method of megasonic cleaningmay include forming microcavitation bubbles in a first room by applyingan electromotive force to a cleaning solution using a megasonic energy,the microcavitation bubbles including stable and unstable bubbles,moving the cleaning solution having the microcavitation bubbles out ofthe first room and to an object to be cleaned, and cleaning a surface ofthe object to be cleaned using the cleaning solution and the stablebubbles.

In accordance with example embodiments, an apparatus for megasoniccleaning may include a bubble generating part, a cleaning part, and aloading part. The bubble generating part may be configured to generatemicrocavitation bubbles that include stable and unstable bubbles byapplying an electromotive force to a cleaning solution using a megasonicenergy and including a container having an inlet line through which thecleaning solution enters the bubble generating part and an outlet linethrough which at least one of the cleaning solution, the stable bubbles,and the unstable bubbles pass. The cleaning part may be configured toreceive the cleaning solution and the stable bubbles from the outletline, the cleaning part being further configured to clean an object tobe cleaned using the cleaning solution and the stable bubbles, thecleaning part being provided separately from the bubble generating part.The loading part may be configured to load the object to be cleaned toclean the object using the cleaning solution and the stable bubbles.

According to example embodiments, there is provided a method ofmegasonic cleaning. In the method, microcavitation bubbles are generatedby applying electromotive force to a cleaning solution using megasonicenergy in a separate room from an object to be cleaned. Themicrocavitation bubbles having a stable oscillation among the formedmicrocavitation bubbles move to the object to be cleaned. A surface ofthe object to be cleaned is cleaned using the microcavitation bubbleshaving a stable oscillation.

In example embodiments, when the microcavitation bubbles having a stableoscillation are moved, the microcavitation bubbles may be controlled, sothat the microcavitation bubbles having an unstable oscillation may becollapsed or removed, thereby preventing the microcavitation bubbleshaving an unstable oscillation from reaching the room where the objectto be cleaned is loaded.

In example embodiments, there may be further included a process forproviding a high frequency oscillation to a room where the object to becleaned may be loaded, so that the microcavitation bubbles, which havemoved to the room, may maintain their stable oscillation state.

In example embodiments, a first power may be applied for producing themicrocavitation bubbles in the separate room and a second power may beapplied for maintaining a stable oscillation of the microcavitationbubbles in the room where the object to be cleaned may be provided.

In example embodiments, the first power may be higher than the secondpower.

In example embodiments, the second power may be less than 50% of thefirst power.

In example embodiments, both of the microcavitation bubbles having astable oscillation and the microcavitation bubbles having an unstableoscillation may be formed by the first power.

According to example embodiments, there is provided an apparatus formegasonic cleaning. The apparatus includes a bubble generating part forgenerating microcavitation bubbles by applying electromotive force to acleaning solution using megasonic energy, and the bubble generating partincludes a container having an inlet line and an outlet line of thecleaning solution. The apparatus also includes a cleaning part forreceiving the cleaning solution that drains through the outlet line andthe microcavitation bubbles having a stable oscillation and for cleaningan object to be cleaned using the microcavitation bubbles having astable oscillation. The cleaning part is provided at a separate placefrom the bubble generating part. The apparatus includes a loading partfor loading the object to be cleaned for cleaning the object using themicrocavitation bubbles having a stable oscillation.

In example embodiments, the bubble generating part may include a firstpiezoelectric transducer for generating the microcavitation bubbles andthe cleaning part may include a second piezoelectric transducer formaintaining the stable oscillation of the microcavitation bubbles.

In example embodiments, the bubble generating part may be provided in aseparate room within the cleaning part or at an outside of the cleaningpart.

In example embodiments, the bubble generating part may be provided in aseparate room within the cleaning part and the cleaning part may includea tank including the cleaning solution and the second piezoelectrictransducer.

In example embodiments, the loading part may be provided within thecleaning part.

In example embodiments, the bubble generating part may be provided at anoutside of the cleaning part and the cleaning part may be a spacebetween the bubble generating part and the loading part.

In example embodiments, the second piezoelectric transducer facing theloading part may be provided on an outer wall of the bubble generatingpart.

In example embodiments, a particle outlet line may be provided fordraining out the cleaning solution including particles. The particleoutlet line may be provided along an outer wall of the container of thebubble generating part and guides the cleaning solution to fill up thecleaning part.

In example embodiments, the inlet line of the cleaning solution may beextended from an outer portion of the cleaning part to an inner portionof the container of the bubble generating part, and the outlet line ofthe cleaning solution may be extended from the inner portion of thecontainer of the bubble generating part to the cleaning part.

In example embodiments, the first piezoelectric transducer may beprovided in parallel or in perpendicular direction with respect to anextended direction of the inlet line of the cleaning solution of thebubble generating part.

In example embodiments, the second piezoelectric transducer may beprovided in parallel or in perpendicular direction with respect to anextended direction of the outlet line of the cleaning solution of thebubble generating part.

In example embodiments, the loading part may make a horizontal rotationor a horizontal and rectilinear movement.

According to example embodiments, the pattern damages of an object to becleaned may be minimized while removing attached particles from theobject to be cleaned. In particular, the particles attached onphotomasks may be removed without damaging patterns formed on theobject, thereby preventing repeated generation of pattern damages onsubstrates due to the attached particles on the photomasks. Thus,manufacturing yield of semiconductor devices may be increased.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings. FIGS. 1 to 9F represent non-limiting, example embodiments asdescribed herein.

FIG. 1 is a flow chart illustrating a method of megasonic cleaning withrespect to an object to be cleaned.

FIG. 2 is a cross-sectional view of an apparatus for performing amegasonic cleaning in accordance with a first example embodiment.

FIG. 3 is a cross-sectional view of an apparatus for performing amegasonic cleaning in accordance with a second example embodiment.

FIGS. 4A to 4C are cross-sectional views illustrating various types ofbubble generating parts applicable in the apparatus illustrated in FIG.3.

FIG. 5 is a cross-sectional view of an apparatus for performing amegasonic cleaning in accordance with a third example embodiment.

FIG. 6 is a cross-sectional view of an apparatus for performing amegasonic cleaning in accordance with a fourth example embodiment.

FIG. 7 illustrates a graph showing a removing efficiency of particles inaccordance with acoustic pressure.

FIG. 8 illustrates a bar graph showing a removing efficiency ofparticles in accordance with various embodiments.

FIGS. 9A to 9F are fluorescent images of particles attached onphotomasks taken after performing megasonic cleaning in accordance withvarious embodiments.

FIG. 10 is a cross-sectional view of an apparatus for performing amegasonic cleaning in accordance with a fifth example embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Various example embodiments will be described more fully hereinafterwith reference to the accompanying drawings, in which some exampleembodiments are shown. The present inventive concept may, however, beembodied in many different forms and should not be construed as limitedto the example embodiments set forth herein. Rather, these exampleembodiments are provided so that this description will be thorough andcomplete, and will fully convey the scope of the present inventiveconcept to those skilled in the art. In the drawings, the sizes andrelative sizes of layers and regions may be exaggerated for clarity.

It will be understood that when an element or layer is referred to asbeing “on,” “connected to” or “coupled to” another element or layer, itcan be directly on, connected or coupled to the other element or layeror intervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on,” “directly connected to”or “directly coupled to” another element or layer, there are nointervening elements or layers present. Like numerals refer to likeelements throughout. As used herein, the term “and/or” includes any andall combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, third etc.may be used herein to describe various elements, components, regions,layers and/or sections, these elements, components, regions, layersand/or sections should not be limited by these terms. These terms areonly used to distinguish one element, component, region, layer orsection from another region, layer or section. Thus, a first element,component, region, layer or section discussed below could be termed asecond element, component, region, layer or section without departingfrom the teachings of the present inventive concept.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting of thepresent inventive concept. As used herein, the singular forms “a,” “an”and “the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. It will be further understood thatthe terms “comprises” and/or “comprising,” when used in thisspecification, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Example embodiments are described herein with reference tocross-sectional illustrations that are schematic illustrations ofidealized example embodiments (and intermediate structures). As such,variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, example embodiments should not be construed as limitedto the particular shapes of regions illustrated herein but are toinclude deviations in shapes that result, for example, frommanufacturing. The regions illustrated in the figures are schematic innature and their shapes are not intended to illustrate the actual shapeof a region of a device and are not intended to limit the scope of thepresent inventive concept.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this inventive concept belongs. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Hereinafter, example embodiments on methods of megasonic cleaning willbe explained in detail.

Megasonic cleaning may be performed by transferring energy generatedfrom a megasonic generator to a fluid body. The main mechanism of themegasonic cleaning may include microcavitation, acoustic streaming,acoustic pressure gradient, pressure enhanced chemical effects, etc. Thecavitation may be defined by rapid formation of minute bubbles fromgases dissolved in fluid body through an application of acoustic energyand collapse of the minute bubbles. The acoustic streaming may representfluid kinetics induced by acoustic waves through the fluid body whenradio frequency (RF) power is applied onto piezoelectric transducer. Themicrocavitation may be a main factor in the megasonic cleaning anddamage generation.

Repeated enlargement and reduction of the microcavitation bubbles makesan oscillation. Detachment torque due to gas/liquid interface sweepingmay be applied onto the particles nearby the oscillation, to therebydetach the particles. The particles far from the oscillation may beremoved by pressure-gradient forces generated from surrounding liquidmaintaining the oscillation due to the oscillating cavitation.

In a middle megasonic power region, patterns may be damaged by implosionof the microcavitation bubbles. That is, when pressure near thecavitations loses symmetrical characteristic in the middle megasonicpower region and is severely deformed, the cavitations may be implodedand vigorous flowing may be generated to damage the patterns. In a highmegasonic power region, a pattern may be damaged due to the chaoticoscillation of the cavitations.

The patterns may be cleaned by a stable and periodic oscillation of themicrocavitation bubbles. That is, particles may be removed from thepatterns by the stable and periodic oscillation of the microcavitationbubbles. In example embodiments, the patterns may be cleaned only by theoscillation of the microcavitation bubbles. That is, particles may beremoved from the patterns only by the action of the oscillation of themicrocavitation bubbles. However, the patterns may be damaged byunstable and irregular behavior of the microcavitation bubbles includingthe implosion and non-linear behavior of the microcavitation bubbles.Therefore, the patterns may be effectively cleaned without damaging thepatterns by using the stable microcavitation bubbles. That is, particlesmay be effectively removed from the patterns without damaging thepatterns by using the stable microcavitation bubbles.

In accordance with example embodiments, stable microcavitation bubblesand unstable microcavitation bubbles may be separated. The unstablemicrocavitation bubbles may be removed and only the stablemicrocavitation bubbles may be used to perform the megasonic cleaning.

FIG. 1 is a flow chart illustrating a method of megasonic cleaning of anobject to be cleaned.

An object to be cleaned may be loaded (Step S10). For example, theobject to be cleaned may be loaded on a loading part of a megasoniccleaning apparatus. The object to be cleaned may be a semiconductorsubstrate or a photomask. Chips may be on the semiconductor substrateand the chips on the semiconductor substrate may be manufactured byusing the photomask. In the manufacturing process, particles may beproduced and attached to the chips or the photomask. These particles maygenerate a defect in the mask or the chips. Accordingly, removing theattached particles, especially from the photomask, may be required.

The object to be cleaned may be loaded in a tank including a cleaningsolution. Alternatively, the object to be cleaned may be loaded on aloading part that is not immersed in the cleaning solution but exposedto the air.

Electromotive force may be applied to the cleaning solution in a bubblegenerating part to generate microcavitation bubbles for cleaning theobject to be cleaned (Step S12). The bubble generating part may beseparated from the loaded place of the object to be cleaned. The bubblegenerating part may be provided with a first transducer for generatingmegasonic of high frequency of about 600 KHz or higher. A first powermay be applied to the first transducer to generate the megasonic. Whenthe electromotive force is received, the cleaning solution may createthe microcavitation bubbles.

In accordance with the application of higher power to the firsttransducer, higher acoustic pressure may be applied to generate moremicrocavitation bubbles. To maximize cleaning efficiency, the number ofthe microcavitation bubbles generated from the bubble generating partshould be increased and the first power applied to the first transducershould be increased.

However, as the power applied to the transducer increases, the number ofunstable microcavitation bubbles having irregular oscillation also mayincrease along with the stable microcavitation bubbles having regularoscillation. The first transducer may be disposed along a vertical orhorizontal direction with respect to an inflowing direction of thecleaning solution in the bubble generating part.

In accordance with example embodiments, the unstable microcavitationbubbles generated from the bubble generating part may not substantiallyfunction to clean the object to be cleaned. Therefore, the first powermay be higher than commonly applied power for the bubble generating partthat produces microcavitation bubbles. The high power may induce patterndefects on the object to be cleaned when the generated microcavitationbubbles are applied directly to the object.

Among the microcavitation bubbles, stable microcavitation bubbles havingperiodic oscillation may be moved to a place where the object to becleaned is placed (step S14). A room where the object to be cleaned islocated may be called a cleaning part. In example embodiments, themicrocavitation bubbles generated by the first transducer may beoutputted through a narrow outlet line and moved to the cleaning part.

During the movement of the microcavitation bubbles from the bubblegeneration part to the cleaning part, the unstable microcavitationbubbles having short lifetimes may be imploded and removed among thegenerated microcavitation bubbles from the bubble generating part. Thus,the unstable microcavitation bubbles may not reach the cleaning partwhere the object to be cleaned is provided. However, the stablemicrocavitation bubbles having relatively long lifetimes may reach theroom where the object to be cleaned is provided. Therefore, only thestable microcavitation bubbles among the microcavitation bubblesgenerated from the bubble generating part may be selected and moved tothe cleaning part.

In this case, the distance from the bubble generating part to the objectto be cleaned may be controlled so that some of all of the unstablemicrocavitation bubbles may be removed while some, all, or most of thestable microcavitation bubbles may reach the object to be cleanedwithout collapse. A width of the outlet line for outputting themicrocavitation bubbles from the bubble generating part, a flowing rateof the outputted microcavitation bubbles, a direction of the inlet lineand the outlet line of the cleaning solution from the bubble generatingpart, a position of the first transducer, etc., may be substantiallycontrolled.

A second power may be provided to the cleaning part to keep theoscillation of the stable microcavitation bubbles that have beentransferred to the cleaning part (step S16). In the cleaning part, asecond transducer may be provided to apply the second power to keep theoscillation stable. The second transducer may be provided along avertical direction or a horizontal direction with respect to theforwarding direction of the microcavitation bubbles flowing from thebubble generating part to the cleaning part.

The second power for keeping the stable microcavitation bubbles may notbe high enough to generate the microcavitation bubbles. The second powermay be lower than the first power. For example, the second power may be50% or less of the first power.

A pathway of the microcavitation bubbles from the outlet line of thebubble generating part to the object to be cleaned may be filled withthe cleaning solution to keep the stable microcavitation bubbles by thesecond power. The stable microcavitation bubbles may flow within thecleaning solution.

It should be noted that not all of the stable bubbles may be used forcleaning the object to be cleaned as some of the stable bubbles mayimplode prior to being used in the cleaning operations or may flowaround the object to be cleaned without cleaning the object. Thus, inexample embodiments, a surface of the object to be cleaned may becleaned using the cleaning solution including some of the stablebubbles.

The object to be cleaned may be loaded within the tank containing thecleaning solution. Alternatively, the object to be cleaned may not beimmersed into the cleaning solution. In this case, the cleaning solutiondrained out from the outlet line may completely fill the space betweenthe object to be cleaned and an outer and lower surface of a nozzle, soas for the microcavitation bubbles to flow in the cleaning solution.

The object to be cleaned may be cleaned using the stable microcavitationbubbles at the cleaning part (step S18).

In accordance with the above-described example embodiment, the particlesattached to the object to be cleaned may be removed using a plurality ofstable microcavitation bubbles having periodic oscillation whilereducing or preventing the pattern damages of the object.

Various apparatuses for megasonic cleaning having various compositionsfor implementing the cleaning method may be illustrated. Exampleembodiments of the apparatuses for megasonic cleaning may be explainedhereinafter.

FIG. 2 is a cross-sectional view of an apparatus for performing amegasonic cleaning in accordance with a first example embodiment.

Referring to FIG. 2, a megasonic cleaning apparatus 100 may include abubble generating part 102 and a cleaning part 110.

The bubble generating part 102 may generate microcavitation bubbles forcleaning an object 30 to be cleaned. The bubble generating part 102 maybe filled with a cleaning solution and may include a container 104having a cleaning solution inlet line 104 a and a cleaning solutionoutlet line 104 b and a first transducer 106. The bubble generating part102 may be positioned at a separate room from a loading part 116 forloading the object 30 to be cleaned.

The cleaning solution may fill the container 104 included in the bubblegenerating part 102. The inlet line 104 a and the outlet line 104 b mayface each other or be provided vertically to each other. Depending on aposition and a diameter of the inlet line 104 a and the outlet line 104b, an amount and a flowing rate of the cleaning solution drained outthrough the outlet line 104 b may be controlled.

The cleaning solution may be a solution used for the megasonic cleaning.The cleaning solution may facilitate a removal of particles from asurface of the object 30 to be cleaned and may prevent the particlesfrom re-attaching onto the surface of the object 30 to be cleaned.

The first transducer 106 may be installed in and on an inner surface ofthe bubble generating part 102 to provide energy for producing themicrocavitation bubbles. The first transducer 106 may be installed alonga direction parallel or vertical to an extended direction of the inletline 104 a. Microcavitation bubbles may be generated by controlling aposition of the first transducer 106.

The cleaning part 110 may be provided separately from the bubblegenerating part 102. The cleaning part 110 may include a cleaning tank111 filled with a cleaning solution and a second transducer 112. Thecleaning solution that drains from the bubble generating part 102through the outlet line 104 b may fill up the cleaning tank 111. Thecleaning solution in the cleaning tank 111 may be the same cleaningsolution filling the bubble generating part 102.

The object 30 to be cleaned may be provided in the cleaning tank 111,and a volume of the cleaning tank 111 may be larger than that of thebubble generating part 102. The cleaning tank 111 may include a particledischarging outlet line 114 for discharging particles separated duringthe cleaning operation.

The second transducer 112 may be provided in the cleaning tank 111 thatis filled with the cleaning solution. The second transducer 112 maymaintain oscillation of the microcavitation bubbles generated by thefirst transducer 106. The second transducer 112 may function to maintaina stable oscillation of the stable microcavitation bubbles among themicrocavitation bubbles generated by the first transducer 106 and maynot generate the microcavitation bubbles. Therefore, power applied tothe second transducer 112 may be lower than the power applied to thefirst transducer 106. The second transducer 112 may be installed in thecleaning tank 111 and on inner surface thereof. The second transducer112 may be provided along a direction vertical to or parallel to theexhausting direction of the microcavitation bubbles from the bubblegenerating part 102.

The outlet line 104 b of the bubble generating part 102 may be extendedto an inside of the cleaning tank 111. The microcavitation bubblesproduced from the bubble generating part 102 and the cleaning solutionmay move through the outlet line 104 b to the inner part of the cleaningtank 111.

The outlet line 104 b may be designed to select the stablemicrocavitation bubbles among the microcavitation bubbles generated fromthe bubble generating part 102 and to guide the stable microcavitationbubbles to the inner part of the cleaning tank 111. A length and adiameter of the outlet line 104 b may be optimized so as to transferonly the stable microcavitation bubbles into the cleaning tank 111. Aposition of the inlet line 104 a and the outlet line 104 b, an inflowingrate of the cleaning solution into the container, a position of thefirst and second transducers 106 and 112, etc., may be adjusted toprevent implosion of the stable microcavitation bubbles transferred tothe cleaning tank 111 and to keep an oscillation of the stablemicrocavitation bubbles in the cleaning tank 111.

Among the microcavitation bubbles generated from the bubble generatingpart 102, stable microcavitation bubbles having relatively longlifetimes may move through the outlet line 104 b to the cleaning tank111 without implosion and nonlinear movement.

The loading part 116 for receiving the object 30 to be cleaned may beprovided in the cleaning tank 111. The object 30 to be cleaned loaded onthe loading part 116 may be disposed facing a draining part of thecleaning solution from the outlet line 104 b, so that the object 30 tobe cleaned may be cleaned by the stable microcavitation bubbles. Theloading part 116 may be designed so as to horizontally rotate the object30 to be cleaned. Alternatively, the loading part 116 may be designed soas to move the object 30 to be cleaned horizontally and rectilineardirection.

According to the cleaning apparatus of the present invention, a largenumber of microcavitation bubbles may be generated from the bubblegenerating part 102 by applying sufficiently high power to maximize asurface cleaning effect of the object 30 to be cleaned. In addition,only the stable microcavitation bubbles among the microcavitationbubbles generated from the bubble generating part 102 may be utilizedfor cleaning the object 30 to be cleaned. Therefore, the pattern damagesof the object 30 to be cleaned may be restrained.

In accordance with the example embodiments, the bubble generating part102 may be provided separately from the cleaning tank 111. The bubblegenerating part 102 may not be immersed into the cleaning solution butonly a portion of the outlet line 104 b may be immersed into thesolution. The bubble generating part 102 may be advantageouslymaintained and repaired since the bubble generating part is locatedoutside of the cleaning tank 111.

FIG. 3 is a cross-sectional view of an apparatus for performing amegasonic cleaning in accordance with a second example embodiment.

Referring to FIG. 3, a megasonic cleaning apparatus 130 may include abubble generating part 132, a second transducer 138 and a loading part140.

The bubble generating part 132 may generate microcavitation bubbles forcleaning an object 40 to be cleaned. The bubble generating part 132 mayproduce stable microcavitation bubbles together with unstablemicrocavitation bubbles.

The bubble generating part 132 may include a container or a nozzlecontaining a cleaning solution for generating bubbles. Since a volume ofthe bubble generating part 132 may be relatively small, the containermay be called as a nozzle 134 in this example embodiment. The bubblegenerating part 132 may also include a cleaning solution inlet line 134a and a cleaning solution outlet line 134 b that are connected to thenozzle 134 and a first transducer 136 for generating the microcavitationbubbles by megasonic action.

The cleaning solution inlet line 134 a may be provided at an end portionof the nozzle 134. The cleaning solution inlet line 134 a has a smallerdiameter or width than that of the nozzle 134. The cleaning solution maybe supplied into the nozzle 134 through the cleaning solution inlet line134 a.

The first transducer 136 may be arranged to generate the microcavitationbubbles from the cleaning solution contained in the nozzle 134. When apower is applied to the first transducer 136 disposed in the nozzle 134having a narrow diameter, a vibration number of a piezoelectricelectrode may be further increased and megasonic having a high frequencymay be generated.

The first transducer 136 may be disposed in a vertical direction to aninflowing direction of the cleaning solution from the cleaning solutioninlet line 134 a in FIG. 3. Alternatively, a location of the firsttransducer 136 may vary within the nozzle 134.

The cleaning solution outlet line 134 b may be provided at another endof the nozzle 134. The cleaning solution and the generatedmicrocavitation bubbles may be drained through the cleaning solutionoutlet line 134 b. A diameter of the cleaning solution outlet line 134 bmay be smaller than that of the nozzle 134. Stable microcavitationbubbles having relatively long lifetimes may be outputted out from thecleaning solution outlet line 134 b. A width and a length of thecleaning solution outlet line 134 b may be adjusted. In addition, aflowing rate of the cleaning solution also may be controlled.

The cleaning solution inlet line 134 a and the cleaning solution outletline 134 b may be provided to face each other in this exampleembodiment. Alternatively, positions of the cleaning solution inlet line134 a and the cleaning solution outlet line 134 b may vary within thebubble generating part 132.

Numbers of the generated microcavitation bubbles and pressure and amountof the cleaning solution may be changed in accordance with positions ofthe first transducer 136, the cleaning solution inlet line 134 a and thecleaning solution outlet line 134 b.

The bubble generating part 132 may not include a bath or a cleaning tankhaving a large volume for containing the cleaning solution in thisexample embodiment.

The object 40 to be cleaned may be cleaned by the stable microcavitationbubbles outputted from the outlet line 134 b at a gap formed between anouter and lower surface of the nozzle 134 and the object 40 to becleaned.

A second transducer 138 making contact with the outlet line 134 b may beprovided at the outer and lower surface of the nozzle 134. The secondtransducer 138 may be disposed in a vertical direction with respect toan extended direction of the outlet line 134 b. The second transducer138 may function to maintain an oscillation of the stablemicrocavitation bubbles drained from the outlet line 134 b.

The oscillation of the microcavitation bubbles may be maintained by thesecond transducer 138, and the object 40 to be cleaned may be cleaned.For the cleaning, the cleaning solution may fill a gap between theobject 40 to be cleaned and the outer and lower surface of the nozzle134.

The object 40 to be cleaned may not make contact with the outlet line134 b. The gap formed between the object 40 to be cleaned and the outerand lower surface of the nozzle 134 may be relatively narrow. When thegap is narrow enough, the cleaning solution that continuously drainsfrom the outlet line 134 b may fill up the gap between the object 40 tobe cleaned and the outer and lower surface of the nozzle 134 without anyseparate container.

A loading part 140 facing the outlet line 134 b may load the object 40to be cleaned. The stable microcavitation bubbles outputted from theoutlet line 134 b may not spread out onto a whole surface of the object40 to be cleaned due to the narrow diameter of the outlet line 134 b.The loading part 140 may be designed to rotate the object 40 to becleaned horizontally. Alternatively, the loading part 140 may also bedesigned to move the object 40 to be cleaned rectilinear and horizontaldirections.

In accordance with this example embodiment, the cleaning may beperformed using the megasonic energy having a high frequency to obtainan excellent cleaning effect.

Positions of the cleaning solution inlet line, the cleaning solutionoutlet line and the transducer of the megasonic apparatus may be changedas described above.

FIGS. 4A to 4C are cross-sectional views illustrating various types ofbubble generating parts that are applicable in the apparatus illustratedin FIG. 3. Some embodiments of the megasonic cleaning apparatuses mayinclude one of the bubble generating parts illustrated in FIGS. 4A to4C.

Referring to FIG. 4A, a bubble generating part 132 a may include acleaning solution inlet line 134 a and a cleaning solution outlet line134 b that faces the cleaning solution inlet line 134 a, in the samemanner as the bubble generating part 132 in FIG. 3. A first transducer136 a may be disposed along a vertical direction to an inflowingdirection of the cleaning solution from the cleaning solution inlet line134 a.

Referring to FIG. 4B, a bubble generating part 132 b may include acleaning solution inlet line 135 a and a cleaning solution outlet line135 b, which may be offset both horizontally and vertically with respectto cleaning solution inlet line 135 a, which is different from thebubble generating part 132 illustrated in FIG. 3. For example, thecleaning solution inlet line 135 a may be oriented horizontally and maybe attached to a side wall of the bubble generating part 132 b and thecleaning solution outlet line 135 b may be orientated vertically and maybe attached to a lower wall of the bubble generating part 132 b, thusthe cleaning solution inlet line 135 a may be offset both horizontallyand vertically with respect to the cleaning solution outlet line 135 b.A first transducer 136 b may be disposed along the same direction as theinflowing direction of the cleaning solution from the cleaning solutioninlet line 135 a. Since a volume of the bubble generating part 132 b maybe relatively small, the container may be called as a nozzle 135 in thisexample embodiment.

Referring to FIG. 4C, a bubble generating part 132 c may include acleaning solution inlet line 135 a and a cleaning solution outlet line135 b, which may be offset both horizontally and vertically with respectto the cleaning solution inlet line 135 a, which is different from thebubble generating part 132 illustrated in FIG. 3. For example, thecleaning solution inlet line 135 a may be oriented horizontally and maybe attached to a side wall of the bubble generating part 132 c and thecleaning solution outlet line 135 b may be orientated vertically and maybe attached to a lower wall of the bubble generating part 132 b, thusthe cleaning solution inlet line 135 a may be offset both horizontallyand vertically with respect to the cleaning solution outlet line 135 b.A first transducer 136 c may be disposed along the vertical direction tothe inflowing direction of the cleaning solution from the cleaningsolution inlet line 135 a. Since a volume of the bubble generating part132 c may be relatively small, the container may be called as a nozzle135 in this example embodiment.

FIG. 5 is a cross-sectional view of an apparatus for performing amegasonic cleaning in accordance with a third example embodiment.

The megasonic cleaning apparatus in accordance with the third exampleembodiment may include the same components in the apparatus illustratedin the second example embodiment except for further including a particleremoving line.

Referring to FIG. 5, a megasonic cleaning apparatus 141 may include abubble generating part 142, a second transducer 148, a particledischarging line 143 and a loading part 145.

The bubble generating part 142 may produce microcavitation bubbles forcleaning an object 50 to be cleaned. The bubble generating part 142 mayinclude almost the same elements as illustrated in FIG. 3. That is, thebubble generating part 142 may include a nozzle 144, a cleaning solutioninlet line 144 a, a cleaning solution outlet line 144 b and a firsttransducer 146.

In accordance with the megasonic cleaning apparatus in this exampleembodiment, the object 50 to be cleaned may be cleaned by stableoscillation of the microcavitation bubbles provided between an outersurface of the nozzle 144 of the bubble generating part 142 and the 50object to be cleaned. During the cleaning process, the cleaning solutionmay fill a gap between an outer and lower portion of the nozzle 144 andthe object 50 to be cleaned.

The particle exhausting line 143 may make contact with outer sidewallsof the nozzle 144. The particle exhausting line 143 may discharge thecleaning solution including the particles to outside after cleaning theobject 50 to be cleaned by the oscillation of the microcavitationbubbles. That is, the cleaning solution including the particles may bedrained out.

The particle exhausting line 143 may be extended from an end portion ofthe outlet line 144 b of the bubble generating part 142 to guide thecleaning solution, so that the cleaning solution may fill up the gapbetween the outer and lower surface of the nozzle 144 and the object 50to be cleaned. In this case, the particle discharging line 143 may bedesigned so that the particle discharging line 143 may not make contactwith the object 50 to be cleaned.

A second transducer 148 making contact with the outlet line 144 b may beprovided at an outer surface of the nozzle 144. The second transducer148 may be disposed horizontally with respect to the outlet line 144 b.The second transducer 148 may maintain a stable oscillation of themicrocavitation bubbles discharged from the outlet line 144 b.

According to another example embodiment, the second transducer 148 maybe provided at an outer wall of the particle discharging line 143 (notshown). In this case, the second transducer 148 may face the outlet line144 b. The second transducer 148 may be parallel to the extendeddirection of the outlet line 144 b.

In this example embodiment, the cleaning solution may be guided by theparticle discharging line 143. The cleaning solution may easily fill upthe gap between the outer and lower portion of the nozzle 144 and theobject 50 to be cleaned without any additional container.

The loading part 145 may load the object 50 to be cleaned so as to facethe outlet line 144 b. The loading part 145 may be designed to make ahorizontal rotation and/or perform scanning. Further, the bubblegenerating part 142 may be designed to perform the scanning.

FIG. 6 is a cross-sectional view of an apparatus for performing amegasonic cleaning in accordance with a fourth example embodiment.

Referring to FIG. 6, a megasonic cleaning apparatus 150 may include acleaning tank 160, a bubble generating part 152, a second transducer 162and a loading part 164.

The cleaning tank 160 may be filled with a cleaning solution. Thecleaning solution may be used for megasonic cleaning. The cleaningsolution may facilitate removing of particles and may preventre-attachment of the particles onto the surface of an object 60 to becleaned. The object 60 to be cleaned may be disposed in the cleaningtank 160, and the surface of the object 60 to be cleaned may be cleanedusing a megasonic cleaning mechanism. The cleaning tank 160 may includethe bubble generating part 152 and the loading part 164, and a volume ofthe tank 160 may be sufficiently large.

The cleaning tank 160 may include a particle discharging line 170 foroutputting particles generated during the megasonic cleaning using themicrocavitation bubbles. The particle discharging line 170 may beextended to outside of the cleaning tank 160 and separated from thesurface of the object 60 to be cleaned.

The bubble generating part 152 may generate microcavitation bubbles forcleaning the object 60 to be cleaned in the cleaning tank 160. Thebubble generating part 152 may include a container 154 including aninlet line 154 a and an outlet line 154 b and a first transducer 156within the container 154.

Particularly, the container 154 may be provided in the cleaning tank150. The inlet line 154 a connected to the container 154 may be extendedto the outside of the cleaning tank 160. Through the inlet line 154 a,the cleaning solution may flow from the outside of the cleaning tank 160into the container 154. A pump may be installed at the cleaning solutioninlet line 154 a to provide the cleaning solution into the container154. The cleaning solution outlet line 154 b for discharging thecleaning solution into the cleaning tank 150 may be connected to thecontainer 154. The inlet line 154 a and the outlet line 154 b may bealigned to face each other and in the same direction or may bevertically offset with respect to one another. The diameters of theinlet line 154 a and the outlet line 154 b may be the same or may bedifferent.

The microcavitation bubbles may be generated from the cleaning solutionsupplied from the inlet line 154 a. The cleaning solution and theoscillation of the microcavitation bubbles may be provided to thecleaning tank 160 through the outlet line 154 b.

The second transducer 162 may be provided in the cleaning tank 160. Thesecond transducer 162 may keep the oscillation of the microcavitationbubbles generated by the first transducer 156. The second transducer 162may not produce the microcavitation bubbles but may keep a stableoscillation of the microcavitation bubbles among the microcavitationbubbles generated by the first transducer 156. Accordingly, a powerapplied to the second transducer 162 may be lower than a power appliedto the first transducer 156. The second transducer 162 may be providedwithin the cleaning tank 160. The second transducer 162 may be disposedin a vertical direction or horizontal direction with respect to theextended direction of the outlet line 154 b. For example, the secondtransducer 162 may be provided at an inner and bottom portion of thecleaning tank 160 as illustrated in FIG. 6. Alternatively, the secondtransducer 162 may be provided at an inner and sidewall portion of thecleaning tank 160.

The loading part 164 for fixing the object 60 to be cleaned may beprovided in the cleaning tank 160. The object 60 to be cleaned may becleaned by a stable oscillation of the microcavitation bubbles among themicrocavitation bubbles generated from the bubble generating part 152.The loading part 164 may be arranged so that the object 60 to be cleanedmay face the outlet line 154 b of the bubble generating part 152.

FIG. 10 is a cross-sectional view of an apparatus for performing amegasonic cleaning in accordance with a fifth example embodiment.

Referring to FIG. 10, a megasonic cleaning apparatus 1150 may include acleaning tank 1160, a bubble generating part 1152, a second and thirdtransducers 1162 and 1163, and a loading part 1164.

The cleaning tank 1160 may be filled with a cleaning solution. Thecleaning solution may be used for megasonic cleaning. The cleaningsolution may facilitate removing of particles and may preventre-attachment of the particles onto the surface of an object 70 to becleaned. The object 70 to be cleaned may be disposed in the cleaningtank 1160, and the surface of the object 70 to be cleaned may be cleanedusing a megasonic cleaning mechanism. The cleaning tank 1160 may includethe bubble generating part 1152 and the loading part 1164, and a volumeof the tank 1160 may be sufficiently large.

The cleaning tank 1160 may include a particle discharging line 1170 foroutputting particles generated during the megasonic cleaning using themicrocavitation bubbles. The particle discharging line 1170 may beextended to outside of the cleaning tank 1160 and separated from thesurface of the object 70 to be cleaned.

The bubble generating part 1152 may generate microcavitation bubbles forcleaning the object 70 to be cleaned in the cleaning tank 1160. Thebubble generating part 1152 may include a container 1154 including aninlet line 1154 a and an outlet line 1154 b and a first transducer 1156within the container 1154.

Particularly, the container 1154 may be provided in the cleaning tank1150. The inlet line 1154 a connected to the container 1154 may beextended to the outside of the cleaning tank 1160. Through the inletline 1154 a, the cleaning solution may flow from the outside of thecleaning tank 1160 into the container 1154. A pump may be installed atthe cleaning solution inlet line 1154 a to provide the cleaning solutioninto the container 1154. The cleaning solution outlet line 1154 b fordischarging the cleaning solution into the cleaning tank 1150 may beconnected to the container 1154. The inlet line 1154 a and the outletline 1154 b may be aligned to face each other and in the same directionor may be vertically offset with respect to one another. The diametersof the inlet line 1154 a and the outlet line 1154 b may be the same ormay be different.

The microcavitation bubbles may be generated from the cleaning solutionsupplied from the inlet line 1154 a. The cleaning solution and theoscillation of the microcavitation bubbles may be provided to thecleaning tank 1160 through the outlet line 1154 b.

The second and third transducers 1162 and 1163 may be provided in thecleaning tank 160. The second and third transducers 1162 and 1163 maykeep the oscillation of the microcavitation bubbles generated by thefirst transducer 1156. The second and third transducers 1162 and 1163may not produce the microcavitation bubbles but may keep a stableoscillation of the microcavitation bubbles among the microcavitationbubbles generated by the first transducer 1156. Accordingly, a powerapplied to the second and third transducers 1162 and 1163 may be lowerthan a power applied to the first transducer 1156. The second and thirdtransducers 1162 and 1163 may be provided within the cleaning tank 160.The second transducer 1162 may be disposed in a vertical direction orhorizontal direction with respect to the extended direction of theoutlet line 1154 b. For example, the second transducer 162 may beprovided at an inner and side portion of the cleaning tank 1160 asillustrated in FIG. 10. The third transducer 1163 may be provided on anouter wall of the bubble generating part 1152 as shown in FIG. 10. Asillustrated, the second and third transducers 1162 and 1163 may provideenergy to the microcavitation bubbles simultaneously on both sides ofthe object 70 to be cleaned which may allow for a more rapid and uniformcleaning. This example embodiment, however, is not limited thereto. Forexample only one of the second and third transducers 1162 and 1163 mayoperate at once rather than both operating simultaneously.

The loading part 1164 for fixing the object 70 to be cleaned may beprovided in the cleaning tank 1160. The object 70 to be cleaned may becleaned by a stable oscillation of the microcavitation bubbles among themicrocavitation bubbles generated from the bubble generating part 1152.The loading part 1164 may be arranged so that the object 70 to becleaned may face the outlet line 1154 b of the bubble generating part1152.

Hereinafter, a cleaning effect in accordance with example embodimentswill be explained comparing with the commonly applied cleaning method.

Experiment on Removing Efficiency of Particles by Acoustic Pressure

Using a conventional megasonic transducer, the oscillation ofmicrocavitation bubbles was generated, and the particles attached onto aphotomask were removed. A power applied to the conventional megasonictransducer was controlled to obtain various values of acoustic pressure.According to the acoustic pressure, the removing efficiency of theparticles was monitored. As the power applied to the conventionalmegasonic transducer increased, the acoustic pressure also increased.The cleaning was performed without flowing cleaning solution.

FIG. 7 illustrates a graph showing a removing efficiency of particles inaccordance with acoustic pressure.

Referring to FIG. 7, a removing efficiency of the particles was onlyabout 22% at the acoustic pressure value of about 68 kPa. However, aremoving efficiency increased to about 97% when the acoustic pressurewas increased to about 114 kPa.

According to the result, it was confirmed that a removing efficiency waslowered at a low acoustic pressure while a removing efficiency wasincreased at a high acoustic pressure. However, when the acousticpressure increases, the degree of the pattern damage may also increasealong with an increase of a removing efficiency of the particles.

Comparative Experiment on Removing Efficiency of Particles

The particles attached onto a photomask were removed by conventionalremoving methods and by methods in accordance with example embodiments.Thus, obtained results were compared.

A cleaning experiment was performed using the apparatus in accordancewith example embodiment 4, illustrated in FIG. 6.

Photomask samples including particles attached thereunto were prepared.A cleaning was performed for each sample by applying a condition asdescribed in the following Table 1.

TABLE 1 Example No. Condition Comparative A power was not applied to thefirst and second transducers Example 1 and a cleaning solution wasflowed. Comparative A power was applied to the first transducer toproduce an Example 2 acoustic pressure of about 197 kPa and a cleaningsolution was flowed. Comparative A power was applied to the secondtransducer to produce an Example 3 acoustic pressure of about 68 kPa anda cleaning solution was stood still. Comparative A power was applied tothe second transducer to produce an Example 4 acoustic pressure of about68 kPa and a cleaning solution was flowed. Example 1 A power was appliedto the first transducer to produce an acoustic pressure of about 114 kPaand to the second transducer to produce an acoustic pressure of about 68kPa and a cleaning solution was flowed.

As described above, only one transducer was used or no transducer wasused in Comparative Examples 1 to 4 for performing the cleaning process.According to Example 1, both of the first and the second transducerswere used to generate an acoustic pressure and the cleaning solution waslet to flow.

FIG. 8 illustrates bar graphs showing a removing efficiency of particlesin accordance with various embodiments. Each bar represents a removingefficiency from the left in accordance with Comparative Example 1 (barI), Comparative Example 2 (bar II), Comparative Example 3 (bar III),Comparative Example 4 (bar IV) and Example 1 (bar V).

Referring to FIG. 8, the removing efficiency of the particles was about97% in accordance with Example 1. In the cleaning part where thecleaning process was performed, an acoustic pressure was only 68 kPa inaccordance with Example 1. However, a removing efficiency was very high.Since the acoustic pressure was not high in the cleaning part, patterndamage due to the acoustic pressure may be reduced.

On the contrary, a sufficient removing efficiency was not obtainable inaccordance with the conventional methods using only one transducer. Anacoustic pressure of about 68 kPa in the cleaning part was too low toobtain a sufficient cleaning effect in accordance with the ComparativeExample 4.

Experiment on Pattern Damages

Evaluation on damages based on an adhesion force of particles wasperformed to estimate damages on photomask patterns. In general, thesmaller the particles attached to the photomask are, the greater theadhesion force is, and thus the small particles may be hardly removed bythe microcavitation bubbles. A size of the particles, which is hard toremove by the microcavitation bubbles, was theoretically calculated andconverted. The particles having a mean diameter of about 48 nm wereobtained and attached onto a surface of the photomask. When these smallparticles attached onto the photomask with a high adhesion force, it maybe considered that the pattern damage on the photomask was generatedsince the adhesion force was strong enough to damage the pattern of thephotomask.

For the particles having a diameter of about 520 nm, a calculatedadhesion torque was about 7×10⁻¹⁶ Nm and a calculated removal torqueapplicable by the cavitation bubbles was about 4×10⁻¹⁵ Nm. Accordingly,the particles having the diameter of about 520 nm were considered as theparticles to be removed and the particles having a diameter of about 48nm were considered to be the patterns formed on the photomask.

Each cleaning experiment was performed using the apparatus in accordancewith example embodiment 4, illustrated in FIG. 6. Each sample wasmanufactured and cleaned according to the following methods described inTable 2.

Sample No. 1 was manufactured by attaching particles having a diameterof about 520 nm onto a photomask. Sample No. 2 was manufactured byattaching particles having a diameter of about 48 nm onto a photomask.

TABLE 2 Example No. Condition Comparative A power was applied to thesecond transducer to produce an Example 5 acoustic pressure of about 68kPa and a cleaning solution was flowed. Comparative A power was appliedto the second transducer to produce an Example 6 acoustic pressure ofabout 197 kPa and a cleaning solution was flowed. Example 2 A power wasapplied to the first transducer to produce an acoustic pressure of about197 kPa and to the second transducer to produce an acoustic pressure ofabout 68 kPa and a cleaning solution was flowed.

FIGS. 9A to 9F are fluorescent images of particles on the photomaskstaken after performing megasonic cleaning in accordance with variousembodiments.

FIGS. 9A to 9C correspond to results obtained using Sample No. 1. FIG.9A illustrates fluorescent particles before performing a cleaningprocess. FIG. 9B illustrates remaining fluorescent particles after acleaning process on the photomask in accordance with Comparative Example5. FIG. 9C illustrates remaining fluorescent particles after a cleaningprocess on the photomask in accordance with Example 2.

Referring to FIGS. 9A to 9C, an improved cleaning efficiency wasobtainable after a cleaning process of Sample No. 1 in accordance withExample 2 when comparing with the result obtained in accordance withComparative Example 5.

FIGS. 9D to 9F correspond to results obtained using Sample No. 2. FIG.9D illustrates fluorescent particles before performing the cleaningprocess. FIG. 9E illustrates remaining fluorescent particles aftercleaning process on the photomask in accordance with Comparative Example6. FIG. 9F illustrates remaining fluorescent particles after cleaningprocess on the photomask in accordance with Example 2.

Referring to FIGS. 9D to 9F, almost all of the particles having adiameter of about 48 nm were not removed but remained after a cleaningprocess of Sample No. 2 in accordance with Example 2. When comparingwith the result obtained after a cleaning process of Sample No. 2 inaccordance with Comparative Example 6, more particles were observed inFIG. 9F. Accordingly, the pattern damage of an object to be cleanedincluding a substrate or a photomask may be reduced when performing amegasonic cleaning process in accordance with the example embodiments.

According to example embodiments, an object to be cleaned may be cleanedby the megasonic cleaning method. A particle removing efficiency may behigh and pattern damage may be reduced. The cleaning method and theapparatus in accordance with example embodiments may be applicable tovarious parts including a semiconductor substrate, a photomask,electronic parts and minute products.

The foregoing is illustrative of example embodiments and is not to beconstrued as limiting thereof. Although a few example embodiments havebeen described, those skilled in the art will readily appreciate thatmany modifications are possible in the example embodiments withoutmaterially departing from the novel teachings and advantages of thepresent inventive concept. Accordingly, all such modifications areintended to be included within the scope of the present inventiveconcept as defined in the claims. In the claims, means-plus-functionclauses are intended to cover the structures described herein asperforming the recited function and not only structural equivalents butalso equivalent structures. Therefore, it is to be understood that theforegoing is illustrative of various example embodiments and is not tobe construed as limited to the specific example embodiments disclosed,and that modifications to the disclosed example embodiments, as well asother example embodiments, are intended to be included within the scopeof the appended claims.

1. An apparatus for megasonic cleaning, comprising: a bubble generatingpart configured to generate microcavitation bubbles in a cleaningsolution by applying an electromotive force to a cleaning solution usinga megasonic energy, the microcavitation bubbles including stable andunstable bubbles, the bubble generating part including a containerhaving an inlet line through which the cleaning solution enters thebubble generating part and an outlet line through which the cleaningsolution passes; a cleaning part configured to receive the cleaningsolution including at least some of the stable bubbles from the outletline, the cleaning part being further configured to clean an objectusing the cleaning solution including at least some of the stablebubbles, the cleaning part being provided separately from the bubblegenerating part; and a loading part configured to support the object inthe cleaning part.
 2. The apparatus of claim 1, wherein the bubblegenerating part includes a first piezoelectric transducer configured togenerate the microcavitation bubbles and the cleaning part includes asecond piezoelectric transducer configured to oscillate the stablebubbles.
 3. The apparatus of claim 1, wherein the bubble generating partis provided one of within the cleaning part and outside the cleaningpart.
 4. The apparatus of claim 3, wherein the bubble generating part isprovided in a separate room within the cleaning part and the cleaningpart includes a tank including the cleaning solution and a secondpiezoelectric transducer.
 5. The apparatus of claim 4, wherein theloading part is provided in the cleaning part.
 6. The apparatus of claim3, wherein the bubble generating part is provided outside the cleaningpart and the cleaning part includes a second transducer between thebubble generating part and the loading part.
 7. The apparatus of claim6, wherein a second piezoelectric transducer is provided on an outerwall of the bubble generating part that faces the loading part.
 8. Theapparatus of claim 6, further comprising: a particle outlet lineconfigured to drain out the cleaning solution including particles, theparticle outlet line being provided along an outer wall of the containerof the bubble generating part.
 9. The apparatus of claim 1, wherein theinlet line through which the cleaning solution enters the bubblegenerating part is extended from an outer portion of the cleaning partto a first inner portion of the container of the bubble generating part,and the outlet line through which the cleaning solution passes isextended from a second inner portion of the container of the bubblegenerating part to the cleaning part.
 10. The apparatus of claim 2,wherein the first piezoelectric transducer is provided in one of aparallel and perpendicular direction with respect to an extendeddirection of the inlet line.
 11. The apparatus of claim 2, wherein thesecond piezoelectric transducer is provided in one of a parallel andperpendicular direction with respect to an extended direction of theoutlet line.
 12. The apparatus of claim 1, wherein the loading partmakes one of a horizontal rotation and a horizontal and rectilinearmovement.
 13. The apparatus of claim 1, further comprising: a firstpiezoelectric transducer in the bubble generating part to generate themicrocavitation bubbles having the stable and unstable bubbles; a secondpiezoelectric transducer in the cleaning part on one side of the object;and a third piezoelectric transducer in the cleaning part on anotherside of the object, wherein the second and third piezoelectrictransducers oscillate the stable bubbles to clean the object.